1. Field Of The Invention
This invention relates to the art of arc welding and more particularly, to a flux-cored wire for gas shielded arc welding which exhibits a good pore formation resistance in gas shielded arc welding of carbon steels and low alloy steels, particularly corroded or paint coated steels.
2. Description Of The Prior Art
In the fields of shipbuilding and bridge construction, titania flux-cored wires have been frequently employed in gas shielded arc welding and, particularly, in carbon dioxide arc welding. This is because the titania-based flux-cored wire makes all position welding at a high efficiency and ensures a good appearance and shape of beads and good welding operability. In order to prevent steel materials from corrosion in the above fields of consumption, however, it is usual to apply, prior to welding, primary rust preventive paints (hereinafter referred to simply as primer) such as wash primers, inorganic zinc primers and the like. This presents the problem that at the time of welding and particularly, fillet welding, pores such as pits, gas grooves and the like are often produced with a lowering of quality and an additional number of steps for re-adjustment.
For solving the above problem, the primer at or around welding portions is preliminarily removed by polishing with a grinder or a paper machine. The polished portion is liable to produce corrosion, thus placing limitation on a storage period not only outdoors, but also indoors.
On the other hand, there has been developed a high hydrogen rate wire having an amount of weld metal-diffusable hydrogen of from 20 to 30 ml/100 grams as a flux-cored wire having a pore resistance against primer-coated steel sheets. In view of the possibility in occurrence of low temperature crack, its application is limited to soft steels and structures wherein a degree of restriction on thin sheets is small.